I just purchased mine in Feb and have enjoyed reading all the information on this site!

I want to see if anyone else experiences the same idle tendencies as mine with a cold start up. It will start up, idle high and steady then slowly go down (not to cold in SoCal). The idle will settle down to steady 500 rpm.

Question is this - it feels like little tremors, random shakes as it idles down. The tach stays steady and no change in rpm with the tremors. But after it settles to regular rpm they are no longer there.

Really hard to say without seeing for myself in person, but sounds perfectly normal really. Unless the car really shakes like its miss-firing or something as it idles down then I doubt it is anything to worry about. Its just little bitty shakes...I wouldn't worry.

I get the same thing. Only does it as it idles down to normal. Has never thrown a code and honestly, it's not very noticable. I'm taking mine to the dealer tomorrow to have a new headlight installed (moisture inside). My cousin works in the service department. I'll ask him. I'm sure they're going to say it's normal or wait for a code. If I have any news, I'll post it.

every GM direct injected vehicles have it. its called cat warm up mode. strictly emission related only to warm up your catalyst converter super fast. it does this by commanding your car's idle to run high super rich, usually at 1k rpm for 20-30 seconds. Just make sure you keep your eye out while in this mode. There's been many guys including myself which include all GM SIDI brands that had their cat warm up mode misfire, causing rough idle, missing, shaking, during this 20-30 seconds. sometimes it will throw an actual misfire codes. There's a TSB for this. it supposed to reflash your ecm with higher idle. Some of us with a tune can't take advantage of this tho... little trembling and just a little shake here and there is completely normal. You will know if your cat warm up mode need attention.

I just purchased mine in Feb and have enjoyed reading all the information on this site!

I want to see if anyone else experiences the same idle tendencies as mine with a cold start up. It will start up, idle high and steady then slowly go down (not to cold in SoCal). The idle will settle down to steady 500 rpm.

Question is this - it feels like little tremors, random shakes as it idles down. The tach stays steady and no change in rpm with the tremors. But after it settles to regular rpm they are no longer there.

I have wondered and felt this exact same thing, I have driven older vehicles that mis-fired and that is the best way to explain it. I understand the fan/idle up and all that but this is a distinct twitch very very similiar to a mis-fire. I have ruled it out but I am going to mention it to my dealer on my first (free) oil change.

It comes and goes meaning it doesn't do this during every cold start. Maybe 2 of 5 times...

I just purchased mine in Feb and have enjoyed reading all the information on this site!

I want to see if anyone else experiences the same idle tendencies as mine with a cold start up. It will start up, idle high and steady then slowly go down (not to cold in SoCal). The idle will settle down to steady 500 rpm.

Question is this - it feels like little tremors, random shakes as it idles down. The tach stays steady and no change in rpm with the tremors. But after it settles to regular rpm they are no longer there.

Anyone else feel this? Is this normal?

Thanks!

Welcome to the forum!! Yes my 2012 shakes from time to time it's normal on these new engines.. Now let's see some pics of your car! : )

Does anyone have any issue with their LFX on cold start where they will get a very high pitched whistle? My LFX has 800 miles on it and its done it for awhile. I don't know if its normal but its definitely an annoyance. It seems to only do it on a cold start though and eventually goes away. The stereo is off, the fans are off so I know there's not interference through there.